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An imaginary number is the product of a real number and the imaginary unit i, [note 1] which is defined by its property i2 = −1. [1][2] The square of an imaginary number bi is −b2. For example, 5i is an imaginary number, and its square is −25. The number zero is considered to be both real and imaginary. [3]
In mathematics, Descartes' rule of signs, described by René Descartes in his La Géométrie, counts the roots of a polynomial by examining sign changes in its coefficients. The number of positive real roots is at most the number of sign changes in the sequence of polynomial's coefficients (omitting zero coefficients), and the difference ...
In number theory, a Descartes number is an odd number which would have been an odd perfect number if one of its composite factors were prime.They are named after René Descartes who observed that the number D = 3 2 ⋅7 2 ⋅11 2 ⋅13 2 ⋅22021 = (3⋅1001) 2 ⋅ (22⋅1001 − 1) = 198585576189 would be an odd perfect number if only 22021 were a prime number, since the sum-of-divisors ...
Complex number. A complex number can be visually represented as a pair of numbers (a, b) forming a vector on a diagram called an Argand diagram, representing the complex plane. Re is the real axis, Im is the imaginary axis, and i is the "imaginary unit", that satisfies i2 = −1. In mathematics, a complex number is an element of a number system ...
t. e. René Descartes (/ deɪˈkɑːrt / day-KART or UK: / ˈdeɪkɑːrt / DAY-kart; French: [ʁəne dekaʁt] ⓘ; [note 3][11] 31 March 1596 – 11 February 1650) [12][13]: 58 was a French philosopher, scientist, and mathematician, widely considered a seminal figure in the emergence of modern philosophy and science. Mathematics was paramount ...
Regulae ad directionem ingenii, or Rules for the Direction of the Mind is an unfinished treatise regarding the proper method for scientific and philosophical thinking by René Descartes. Descartes started writing the work in 1628, and it was eventually published in 1701 after Descartes' death. [1] This treatise outlined the basis for his later ...
The imaginary unit i in the complex plane: Real numbers are conventionally drawn on the horizontal axis, and imaginary numbers on the vertical axis. The imaginary unit or unit imaginary number (i) is a solution to the quadratic equation x2 + 1 = 0. Although there is no real number with this property, i can be used to extend the real numbers to ...
[2] [3] The adjective real, used in the 17th century by René Descartes, distinguishes real numbers from imaginary numbers such as the square roots of −1. [4] The real numbers include the rational numbers, such as the integer −5 and the fraction 4 / 3. The rest of the real numbers are called irrational numbers.